18.3 Emergency Descent, Engine Failure, and System Malfunctions
Key Takeaways
- 91.3 makes the PIC directly responsible and the final authority; in an in-flight emergency requiring immediate action the PIC may deviate from any Part 91 rule to the extent required, and sends a written report only if the Administrator requests one.
- Emergency descent (ACS PA.IX.A) is for fire, smoke, or — in pressurized airplanes — rapid decompression; trainers usually mean cabin fire or smoke. Use the AFM configuration and a bank to steepen the descent without exceeding airframe limits.
- Engine failure after takeoff: pitch immediately for best glide, land ahead if low, and treat a turnback as a trained judgment call at a safe altitude — not a reflex. The common A-B-C-D aid (airspeed, best field, checklist, declare) tracks the Airplane Flying Handbook order.
- Partial power, electrical or cabin fire, vacuum failure, an open door, and trim runaway are AFM-checklist problems; fly the airplane first and do not invent a generic boldface.
- Declare on 121.5 MHz and squawk 7700 when you need priority; MAYDAY is distress, PAN-PAN is urgency.
ACS PA.IX.A (emergency descent), PA.IX.B (emergency approach and landing), and PA.IX.C (systems and equipment malfunctions) are procedure items. The written test will not fly your 172. It will ask who may break a rule, when you descend as an emergency, what you do first after the engine stops, and whether you invent a checklist. Airplane Flying Handbook (AFH) Chapter 18, the AFM/POH for that airplane, AIM Chapter 6, and 14 CFR 91.3 are the sources.
91.3, 7700, and 121.5
91.3(a): the PIC is directly responsible for, and the final authority as to, the operation of that aircraft. 91.3(b): in an in-flight emergency requiring immediate action, the PIC may deviate from any rule of Part 91 to the extent required to meet that emergency. 91.3(c): if you used (b), you send a written report only upon the request of the Administrator — not automatically, and not because a controller sounded unhappy. ATC cannot countermand a 91.3(b) deviation they do not understand in the moment; they can help you once you talk.
Tell the system you are an emergency. Squawk 7700. Guard is 121.5 MHz (and 243.0 MHz on military UHF). MAYDAY three times is distress — you are threatened by serious or imminent danger and need immediate help (engine out, fire, forced landing). PAN-PAN is urgency — a condition concerning safety that does not yet require MAYDAY (a sick passenger, a sick engine that is still making partial power). Use plain language after the call: who you are, where you are, what you need, how many souls, fuel in hours if you know it. If you can only do one radio thing, 7700 plus a brief 121.5 call beats a long story on a crowded tower frequency while the airplane is still descending through a bad attitude.
Emergency descent — PA.IX.A
An emergency descent is a maximum-rate, controlled descent to a safe altitude. AFH situations are cockpit or cabin fire or smoke, and, in pressurized airplanes, rapid decompression. A typical PAR trainer is not pressurized. For you, the knowledge-test picture is fire or smoke, not a routine “I want to get down faster” descent.
Configuration is whatever that AFM says. A common light-airplane setup is throttle idle, propeller high RPM if you have a constant-speed prop (more drag), mixture as the checklist specifies, and gear and flaps only inside their airspeed limits. AFH has you bank (often about 30° to 45°) so the descent steepens, the load factor stays positive, and you can clear the windshield to look for traffic. Do not dive through Vne or a flap/gear limit because a memory aid said “max drag.” Pitch for the AFM airspeed, not for a vertical-speed number you liked in the simulator. If the emergency is fire, the descent is toward a landing, not a cruise altitude where you “see if it gets better.” Notify ATC when the airplane is under control. A long idle descent on a healthy engine is a different maneuver; do not confuse it with a fire descent and then “clear the engine” while the cabin is still burning.
Engine failure after takeoff — fly, then decide
When the engine stops, attitude and airspeed first. Lower the nose and capture best-glide (the AFM number, often near L/Dmax; many 172s publish about 68 KIAS clean — use the placard in that airplane). A climb attitude with a dead engine is a stall at 300 feet AGL.
If you are low, AFH is not romantic: continue ahead or slightly left or right into the best available area. A takeoff into a headwind already pointed you at the lowest groundspeed landing. Turning around to a runway behind you — the “impossible turn” — costs altitude in the turn, more altitude to roll out, and still leaves you with a downwind landing toward the departure end. AFH says a pilot who tries it without due consideration and training will need considerable luck. AC 61-83 now tells instructors to teach when a turnback can be safe in a specific make and model. That is a judgment and training topic, not a dare and not a PAR instruction to “always come back at 400 feet.” If you have not practiced the altitude loss in that airplane, the written-test answer is land ahead.
Once the nose is down and the wings are flying, a widely taught memory aid that follows the AFH order is A-B-C-D:
| Letter | Meaning | What it prevents |
|---|---|---|
| A | Airspeed — best glide, then trim | Stalling while you troubleshoot |
| B | Best field — size, surface, wind, obstacles, people | Stretching a glide to a pretty airport you cannot reach |
| C | Checklist — AFM restart or secure items | Invented flows that skip fuel selector or carb heat |
| D | Declare — 7700, 121.5 or the frequency you are on | Silent emergencies that nobody is vectoring around |
Some schools add E for execute / ELT. Use it if it helps; do not skip A to get to the radio. A restart checklist is for altitude you actually have. Below a few hundred feet, the checklist is “fly the forced landing.” Partial power is still an emergency: a rough engine that might carry you to a runway can also quit over the last row of trees. Point at a real field while you troubleshoot, and do not fly a sick engine over worse terrain to “make it home.”
System malfunctions — AFM first, not invented boldface
PA.IX.C will name a failure and ask for the decision process. The process is: fly the airplane, identify, open the AFM/POH emergency section, do those items, then land as the checklist and the situation require. Do not memorize a generic “all airplanes” boldface that contradicts the book in the seat-back pocket.
- Electrical fire / smoke. Typical AFM path: master off, other electrical loads off, vents/heat as directed (often closed to starve a cockpit fire, then cracked to vent smoke), extinguisher if you have one, then restore only what you need, one item at a time, to isolate the circuit. Land. Do not keep resetting a popping breaker into a burning wire.
- Cabin / heater fire. Heat off if an exhaust muff is involved (that is also the carbon monoxide move from Chapter 17), extinguish, vent as the checklist says, land. Know where the extinguisher actually is before the flight.
- Vacuum or instrument failure. The attitude and heading indicators that live on vacuum will lie and then die. Fly partial panel: turn coordinator, magnetic compass, pitot-static airspeed/altimeter/VSI. Get VMC and land. Do not chase a tumbling AI into a graveyard spiral.
- Door or window open. This is usually noise and a draft, not a departure from controlled flight. Fly first. Do not unbuckle and dive across the cabin. Slow to any AFM recommended speed, land, and latch it on the ground. DECIDE’s Estimate step is the whole skill: the risk rank is different in IMC than in a 1,500-foot VFR climb.
- Trim or autopilot runaway. Hold the nose with whatever force it takes, disengage the autopilot, pull the trim / autopilot circuit breaker if the AFM identifies it, and fly with the remaining manual force. Land. Do not let go to “see if it stops.”
Scenario: DeShawn, 400 feet, and the turnback
DeShawn’s 172 loses the engine at 400 feet AGL after takeoff. Houses are slightly left; a fairway is mostly ahead. He has watched videos of a 180-degree turnback and thinks macho plus YouTube is a procedure. AFH wants the nose down to best glide and a landing ahead on the fairest surface he can reach. A turnback at that height, unpracticed in that airplane, is the impossible-turn accident report. If the same failure happens at a height he and his instructor have measured and briefed for this model, with a turn already planned into the wind, that is a different Estimate. The knowledge-test default remains: airspeed, field ahead, AFM items you have time for, declare. 91.3 lets him land on the fairway. It does not require a written report unless the FAA asks.
In a typical unpressurized trainer, when is an emergency descent the ACS/AFH maneuver, and how is it flown?
An engine fails shortly after takeoff at a low altitude with no runway remaining. What does the Airplane Flying Handbook want first?
During an in-flight emergency a private pilot deviates from a Part 91 traffic-pattern altitude to reach a suitable field. Which statement is correct?